Jumping dead battery
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Joined: Jan 2000
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From: Metro Detroit (Redford)
Jumping dead battery
What actually happens when you jump a dead battery? It makes sense that the dead vehicle is starting off the good vehicle's battery, but then it should start right up. Often it does not, which makes me suspect that a little recharging of the dead battery is necessary. Perhaps initially the dead battery is drawing off from the good battery and thereby starving the starter of the dead vehicle then after the dead battery gets some juice the starter gets enough to work? That would explain the following: Yesterday I jumped my boss (he left his lights on all day). His battery is probably on its last legs. We had a good contact, lots of sparks on last cable hookup. All it did was click every time he tried the starter. We let it run 5 minutes and then it started. Meanwhile, when he would try the starter my volt gauge would dip from 14 to about 10/11. That would make sense for battery voltage, but I understand when my engine is running the volt gauge gives alternator output, not battery voltage.
If the dead battery hinders the dead vehicle from getting full use of the good battery, then it would make sense to disconnect the dead battery and hook directly to the disconnected cables.
If the dead battery hinders the dead vehicle from getting full use of the good battery, then it would make sense to disconnect the dead battery and hook directly to the disconnected cables.
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Joined: Nov 2000
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Jumping dead battery
Paul, I think what's happening is you are actually recharging the battery, similar to a battery charger you use at your house or for your cell phone, etc. You're basically plugging it it using the other car's battery as a power source to recharge. I'm pretty sure if you jumped a car and left the cables on for several hours with the good car running and the old one turned off, you could maybe almost fully charge the battery. That's why when you jump someone, you let it run for 5 minutes and then they try it, and it starts, and then they let it run for a while. This is because your battery is done doing the work to turn the motor over, but now your alternator constantly recharging the battery and running the car's power. It's like, if you have a dead battery or dead cell, or think you do, you can take it to NTB and they will hook it up to a charger for 24 hours to either A) fully recharge it, or B) restore the dead cell, if it is salvageable. Heck, sure beats $80 for a new battery when you can have that done for free!
Ryan
Ryan
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Joined: Apr 2001
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Jumping dead battery
The battery is a storage well for electrical current, which is measured in amperes. A dead battery is an empty well and any current flowing toward it takes the path of least resistance first and flows thusly into the well, as water would in a similar fashion. This damps the available current from the donor battery until such point as the dead battery has gained an amount of amps equal to or greater than the amount required to turn the starter.
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From: Inthepast
Jumping dead battery
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Eliminating the dead battery and hooking the cables direct to the vehicle requiring the jump usually doesn't work. Too much resistance for the "good" juice to flow through. I have sometimes taken the good battery out and installed that in the dead car then switch back. It's often hard to do that nowadays because the batteries are often not the same and even if they are, ever try to remove a battery in the parking lot? You almost need a full tool set! :-)
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[LINK:www.ford-trucks.net/users/stockman|Stockman's Club FTE Site]
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Eliminating the dead battery and hooking the cables direct to the vehicle requiring the jump usually doesn't work. Too much resistance for the "good" juice to flow through. I have sometimes taken the good battery out and installed that in the dead car then switch back. It's often hard to do that nowadays because the batteries are often not the same and even if they are, ever try to remove a battery in the parking lot? You almost need a full tool set! :-)
[/FONT]
https://www.ford-trucks.com/dcforum/User_files/StockMan/flag.gif[br][FONT COLOR="#ff0000" SIZE="+2" FACE="Bassett"]Stock Man[/FONT]
[FONT COLOR="#0000ff" SIZE="+1" FACE="Tahoma"]
[LINK:www.ford-trucks.net/users/stockman|Stockman's Club FTE Site]
[LINK:www.67fordtruck.com|1967 F-Series Registry ( www.67fordtruck.com )]
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